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Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

Fill in the blanks:
1 psi is equivalent to $-$ atmospheric pressure.

  1. $34.046\times 10^{-3}$

  2. $64.046\times 10^{-6}$

  3. $24.046\times 10^{-3}$

  4. $68.046\times 10^{-3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Psi stands for pound force per square inch. 

Normal atmospheric pressure is 14.7psi.
         $14.7psi=1$ atmospheric pressure

         $1psi=68.027\times10^{-3}atm$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

In free space, Fortin's barometer will read:

  1. $0\ mm$ of Hg

  2. $76\ cm$ of Hg

  3. $1\ cm$ of Hg

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fortin's barometer is a modified form of Torricelli's barometer which is used to measure atmospheric pressure. In free space there is no matter (no atmosphere) therefore no atmospheric  pressure hence barometer will read 0mm of Hg .

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

The pressure of a gas filled in the bulb of constant volume gas thermometer at $0^0C$ and $100^0C$ are 28.6 cm and 36.6 cm of mercury respectively. The temperature of bulb at which pressure will be 35.00 cm of mercury will be:

  1. $80^0C$

  2. $70^0C$

  3. $55^0C$

  4. $40^0C$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

from$T=\dfrac{p-p _0}{p _{100}-p _0}\times 100^0=\dfrac{35-28.6}{36.6-28.6}\times 100^0=80^0$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

The pressure of a gas filled in the bulb of a constant volume gas thermometer at $0^o$C and $100^o$C are $28.6cm$ and $36.6cm$ of mercury respectively. The temperature of bulb at which pressure will be $35.0cm$ of mercury will be 

  1. $80^o$C

  2. $70^o$C

  3. $55^o$C

  4. $40^o$C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
In a constant volume gas thermometer, the pressure of the gas varies in proportion to the temperature of the gas. The temperature varies linearly wrt to the pressure and vice versa.

 So the formula is:   $ T = \dfrac{(P - P _{0})}{(P _{100} - P _{0})}\times 100^\circ C$

     Where $T$ is the temperature at pressure $P$.
                $P _0$ is pressure at $T _0 = 0^\circ C$ 
             and $P _{100}$ is pressure at $T _{100} = 100⁰C$
                 
   $T = \dfrac{(35.0 - 28.6)}{(36.6 - 28.6)}  \times 100 ^\circ C$  
     
$  = 80^\circ C$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

Two communicating cylindrical vessel contain mercury. The diameter of one vessel is n times larger than the diameter of the other.A column of water of height h is poured into the vessel.The mercury level will rise in the right - hand vessel (s=relative density of mercury and p = density of water ) by 

  1. $ \frac { n^ h }{ (n\quad +\quad 1)^ 2s } $

  2. $ \frac { h }{ (n^ 2\quad +\quad 1)s } $

  3. $ \frac { h }{ (n\quad +\quad 1)^ 2s } $

  4. $ \frac { h }{ (n^{ 2 }s) } $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is given that the diameter of one vessel is n times larger than the diameter of other. So,

$ \pi {{r}^{2}}{{h} _{1}}=\pi {{(nr)}^{2}}{{h} _{2}} $

$ {{h} _{1}}={{n}^{2}}{{h} _{2}} $

Since, pressure at point A is equal to pressure at B

$ \rho gh=({{h} _{1}}+{{h} _{2}})\rho 'g $

$ \because s=\dfrac{\rho '}{\rho } $

$ \rho gh=({{n}^{2}}{{h} _{2}}+{{h} _{2}})s\rho g $

$ {{h} _{2}}=\dfrac{h}{({{n}^{2}}+1)s} $

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

A thin tube sealed at both ends, is $100\ cm$ long. It lies horizontally, the middle $0.1\ m$ containing mercury and the two ends containing air at standard atmospheric pressure. If the tube is turned to a vertical position, by what amount will the mercury be displaced ?

  1. $1.84\ cm$

  2. $8.45\ cm$

  3. $2.95\ cm$

  4. $5\ cm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the tube is vertical, the pressure difference between the two air columns must balance the weight of the mercury column. Using Boyle's Law for both air columns, we find the displacement of the mercury.

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

A barometer tube reads $76$ $cm$ of mercury. If the tube is gradually inclined at an angle of $60 ^ { \circ }$ with vertical, keeping the open end immersed in the mercury reservoir, the length of the mercury column will be  

  1. $152 \mathrm { cm }$

  2. $76 \mathrm { cm }$

  3. $\dfrac{76cm}{sin30^o}$

  4. $38 \mathrm { cm }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The vertical height of the mercury column in a barometer is independent of the tube's inclination, provided the reservoir is open to the atmosphere. The length of the mercury column along the tube will increase, but the vertical height remains 76 cm.